The Moon’s an arrant thief, and her pale fire she snatches from the Sun

Well, not all of it. Some of the Moon’s pale fire is actually snatched from cosmic rays, as seen in the Astronomy Picture of the Day from last Friday.

Gamma-ray Moon
This is an image of the Moon in gamma rays, taken by NASA’s EGRET telescope. The gamma rays are produced by cosmic rays (which aren’t electromagnetic radiation at all, but mostly high-energy protons) striking the lunar surface. There is no equivalent process for the Sun, and in fact the Moon is much brighter than the Sun in gamma rays.

The Sun has some tricks of its own, of course. The Moon picture reminded me a bit of this one:

Neutrino Sun
They’re both circular false-color blobs, so I suppose the resemblance isn’t so surprising. But this is an image of the Sun in neutrinos, reconstructed using data from the Super-Kamiokande neutrino detector in Japan. (Yes, the one that was essentially destroyed in a freak accident. But it’s now back online, and meanwhile I’m sure Koshiba’s Nobel Prize was some consolation.) The Sun, of course, makes its own neutrinos, but it’s amazing that we can actually image a celestial object using something other than photons!

Besides photons, cosmic rays, and neutrinos, there aren’t that many ways we get to observe the universe. I’m looking forward to the first images of either the Sun or Moon in gravitational waves.

Update: As Alex R. mentions in the comments, Ray Davis passed away on Wednesday. He was the pioneer in solar-neutrino measurments, overseeing the Homestake mine experiment, and shared the Nobel with Koshiba.

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19 Responses to The Moon’s an arrant thief, and her pale fire she snatches from the Sun

  1. Spatulated says:

    Hopefully i will be doing things like that, i am going into imaging sciences next year! woohoo

  2. Cynthia says:

    Sean…Thanks for sharing these images of “the Moon in gamma rays” versus “the Sun in neutrinos.” These images remind me of a depiction of the “Moon in polarization” presented by John Carlstrom in a talk at Fermilab. Furthermore, he made the following “off-the-cuff” comment: perhaps – due to the Moon’s strong connotations of romance, he receives more requests for the DASI/Moon polarization than the DASI/CMB polarization. Finally, I must agree the Moon with a gravitational signature would be an ultimate symbol of lunar romance!

  3. Plato says:

    A statement on satellite travel? Would that benefit perspective about these “relations of Sun and moon” in gravitational waves? Hmmm….Qui? NON!

    IN regards to “Langrangian perspective” I think we can already do this?

    But as to making “conceptual leaps,” the views of earth are now not so smooth as seen below.:) How would this be applicable to the moon? I wonder:)

    Density fluctuations on the surface of the Earth and in the underlying mantle are thus reflected invariations in the gravity field.As the twin GRACE satellites orbit the Earth together, these gravity field variations cause infinitesimal changes in the distance between the two. These changes will be measured with unprecedented accuracy by the instruments aboard GRACE leading to a more precise rendering of the gravitational field than has ever been possible to date.

  4. spyder says:

    The first words out of my mouth were: “holy crap, this is way cool” Thanks. Wow!

  5. Mark says:

    I agree Spyder. Whenever I’ve seen neutrino photos like this at conferences I’ve always had the same response.

  6. PK says:

    Yeah, this is fantastic! So what other bright neutrino sources are out there? Would a map of the sky be interesting, or are there not enough localised sources?

  7. Kea says:


    Thank you for the title to this thread. Just beautiful, despite it’s evil intentions.

  8. anon says:

    Very cool images. And an equally cool post title.

    pada ata lane pad not ogo old wart alan ther tale feur far rant lant tal told

  9. Kea says:

    ‘Tis in the malice of mankind, that he thus advises us not to have us thrive in our mystery

  10. Sean says:

    PK, so far (I hope I’m not embarassing myself here by missing something) there have only been two extraterrestrial neutrino sources ever detected — the Sun, and a brief burst from Supernova 1987a. So, with the current state of detector technology, a map would not be very enlightening. If I understand correctly, both the AMANDA experiment:

    and its successor IceCube:

    both in Antarctica, have detected neutrinos, but they are probably secondaries produced when cosmic rays hit the atmosphere, not neutrinos from space. But I could be wrong about that, and someone who knows should chime in. We certainly hope that IceCube and other experiments will be detecting extraterrestrial neutrino sources soon.

  11. Plato says:

    Pierre Auger on Cosmic Rays:

    “For in 1938, I showed the presence in primary cosmic rays of particles of a million Gigavolts — a million times more energetic than accelerators of that day could produce. Even now, when accelerators have far surpassed the Gigavolt mark, they still have not attained the energy of 1020eV, the highest observed energy for cosmic rays. Thus, cosmic rays have not been dethroned as far as energy goes, and the study of cosmic rays has a bright future, if only to learn where these particles come from and how they are accelerated. You know that Fermi made a very interesting proposal that particles are progressively accelerated by bouncing off moving magnetic fields, gaining a little energy each time. In this way, given a certain number of “kicks,” one could perhaps account for particles of 1018 — 1020 electron volts. As yet, however, we have no good theory to explain the production of the very-high-energy particles that make the air showers that my students and I discovered in 1938 at Jean Perrin’s laboratory on a ridge of the Jungfrau.”

    — Pierre Auger, Journal de Physique, 43, 12, 1982

    The highest energy particle ever observed was detected by the Fly’s Eye in 1991. With an energy of 3.5 x 1020eV (or 56J), the particle, probably a proton or a light nucleus, had 108 times more energy than particles produced in the largest earth-bound accelerators. The origin of the particle is unknown. At such a high energy, and with its assumed charge, the path of this particle through the cosmos would have been relatively unaffected by galactic and intergalactic magnetic fields. Yet no plausible astrophysical source is known along the arrival direction, within the maximum possible source distance imposed by collisions with photons of the cosmic microwave background. This event remains a mystery! It is clear that it existed, but there is no obvious explanation for its source.

  12. Cygnus says:

    This stuff is really cool! Though, for the neutrino image of the sun, does anybody have any idea of how statistically significant the image is?

  13. Amara says:

    Regarding neutrino detections, I’m not a neutrino astronomer, but haven’t cosmic ray neutrinos been detected? There seems to be attention and experiments. (Even searching for radio signals from UHE neutrino interactions on the moon!)

  14. Sean says:

    Amara, by “cosmic ray neutrinos” I think one means “neutrinos that are produced when cosmic rays hit the atmosphere.” But as for actual neutrinos that traveled a long way through space before being detected here on Earth, the Sun and SN 1897a are the only sources. So far!

  15. ed hessler says:

    I’ve been so much in awe of these photographs that I decided silence was best. Appreciate seems to be the order of the day. However, on the other hand, as scientists araound the world are known to say, sometimes too often for policy wonks, I want to add my thanks for the photographs, one of which I’d seen a few days ago, for your comments as well as for the comments by respondents. These pictures raise a question that I think about from time-to-time: what does it mean to observe something? Makes me want to say, C’mon gravity!

  16. Alex R says:

    I’ll use this relatively recent solar neutrino post to note the passing of Ray Davis, who, of course, created the experiment that first detected solar neturinos, and who first noticed the fact that a lot of those neutrinos were missing. (He shared the Nobel with Koshiba, mentioned in your post.)